As a means for feeding sheets of corrugated cardboard one sheet after another to a machine such as an automatic box-making machine, there is known a device which consists of a frictional conveyor belt driven in the one direction, a control plate located above said frictional conveyor belt and a positioning means for stacking sheets of cardboard on said frictional conveyor belt behind said control plate, whereby upon the movement of said frictional conveyor belt the bottommost sheet of cardboard in said stack is fed forward, slipping under said control plate.
In said known device, however, when a warped sheet of cardboard happens to be included in the stack or the whole stack happens to be warped, the sheet of cardboard to be fed forward will be obstructed by the control plate and, being unable to slip under said control plate, it will cause trouble with the cardboard feeding. Especially when the stack is small, the pressure acting on the bottommost sheet of cardboard will be smaller than when the stack is high. Therefore, there is little likelihood that warping of the bottommost sheet of cardboard will be corrected by the weight of the stack, and the feeding of the sheets will often be improper.
In view of this problem with the conventional device, there has been a demand for a cardboard sheet-feeding device equipped with a cardboard-holding mechanism which makes it possible to correct the warping of the sheets of cardboard irrespective of the height of the stack, thereby ensuring smooth feeding of the sheets of cardboard.